The cases of puncturing a blood vessel with a hollow needle include a case of puncturing a vein and a case of puncturing an artery, depending on the purpose of puncturing, such as collecting blood, insertion of a catheter, etc. When a blood vessel is punctured, blood flows into a puncture tool such as a transparent syringe. A skilled person can judge whether the blood obtained is venous blood or arterial blood, based on the color of the blood obtained. However, it may be difficult for an unskilled person to make such a judgment.
Since oxygen saturation of blood is low in veins and high in arteries, whether the blood obtained is venous blood or arterial blood can be determined also by measuring the oxygen saturation of the blood obtained. Measurement of the oxygen saturation can be made, for example, by use of a measuring instrument described in Japanese Laid-Open Patent Publication No. 2006-288835. In this instrument, light emitted from a light emitting element is transmitted through blood (the measurement object) before being received by a light receiving element, and whether the blood is venous blood or arterial blood can be determined based on the band characteristic of the wavelength of the light received. By use of a device based on such a principle, even an unskilled person can easily judge whether the blood obtained is venous blood or arterial blood, which is convenient.
In medical procedures, for example, during a surgical operation, the operating surgeon and the like who make direct contact with a patient are, in principle, permitted to touch only medical instruments that have been sterilized.
However, the device described in the above-mentioned Japanese Laid-Open Patent Publication No. 2006-288835 has the light emitting element, the light receiving element, a power supply, a control unit, etc. and is therefore difficult to sterilize; accordingly, the device cannot be used as it is for a surgical operation or the like.